Abstract: Two spindles are provided that are coaxial. The head-stock carrying one spindle can move on longitudinal slideways which are parallel to the axis of the spindles. That provides, with a synchronization of the speeds of the spindles to effect the transfer of the workpieces from the chuck of one spindle onto the chuck of the other spindle. A carriage provided with a transversal slideway can move along a pair of longitudinal slideways, parallel to the axis of the two spindles. This carriage carries a frame provided with a revolver-turret-carrying working-tools. The tools of the two revolver-turrets thus can work indifferently the workpieces carried by one and the other of the two spindles.